To ensure gas seal and electric connection in a solid electrolyte-type fuel cell (SOFC) having solid electrolyte layers, it has been proposed to prepare two kinds of catalyst layers in thick rectangular plate shapes and formed with gas passages except for peripheral portions thereof, to arrange the catalyst layers at both surfaces of each solid electrolyte layer, respectively, to arrange current collector layers at outer surfaces of the catalyst layers, respectively, to plurally stack such arranged structures so as to constitute a fuel cell stack, and to apply a large load to the fuel cell stack in the stacking direction thereof.
Particularly, because materials such as yttria-stabilized zirconia (YSZ) to be used as solid electrolyte layers are extremely brittle in SOFC which operates at high temperature, it has been proposed to adopt thick members as the solid electrolyte layers on the order of millimeter inclusive of associated neighboring members and in order to attain a strength against thermal stress.
U.S. Pat. No. 6,344,290 discloses a constitution to form the whole of fuel cell into a donut shape and to supply the gases through the central portions of the donut, so as to deal with thermal stresses. Concretely, at that region of the donut outside the central portions for supplying the gases, there are successively formed an anode substance layer, a solid electrolyte layer, and a cathode substance layer on a porous electric-conductor layer. Further, such structures are stacked via corrugated gas separators, respectively, to thereby constitute a fuel cell stack. It is further intended to ensure the electric connection of the whole of the fuel cell stack including electric-power generating regions having the anode substance layers, solid electrolyte layers and cathode substance layers, respectively, by applying a stacking directional pressure to the fuel cell stack.